Notching the first pole piece of a write head with a notching layer in a combined magnetic head

ABSTRACT

In the manufacture of a combined magnetic head, milling time for notching a first pole piece of the head&#39;s write element is reduced by constructing the first pole piece with a notching layer on a first pole piece layer, the notching layer having first and second corners adjacent first and second side walls of the second pole tip. The first pole piece layer has a wide lateral expanse, and the notching layer has a narrow lateral expanse. The width of the notching layer is preferably 0.2 μm to 2.0 μm wider than a target track width of the second pole tip. With this arrangement, the notching layer has first and second side walls that project 0.10 μm to 1.0 μm, laterally, beyond first and second side walls, respectively, of the second pole tip. The thickness of the notching layer is preferably between 0.1 μm to 1.0 μm. Accordingly, full notching of the notching layer can be achieved by milling a small corner in a range of 0.10 μm by 0.10 μm to 1.0 μm by 1.0 μm, as seen in an ABS view. The gap layer is formed on the notching layer, followed by forming the second pole tip on the gap layer. Milling at an angle is then employed to mill through the gap layer and notch the notching layer. In comparison to milling a prior art large lateral expanse of the first pole piece to achieve notching, milling the small corner of the notching layer requires a very short milling time. This results in less consumption of the second pole tip, so that better control of a final track width can be accomplished. Also, since there is less consumption of the top of the second pole tip, the aspect ratio of photoresist employed to construct the second pole tip is reduced, so as to enhance the line width of the second pole tip. Further, there is less redeposited material to clean up after the milling cycle. All of these factors reduce the process time and increase manufacturing throughput.

CROSS REFERENCE TO RELATED PATENTS

Cross reference is made to commonly assigned U.S. Pat. No. 5,438,747 andcommonly assigned U.S. Pat. No. 5,452,164 which are incorporated byreference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a merged MR head made by notching thefirst pole piece of the head's write element and also to forming anotched first pole piece with a first pole piece layer and a notchinglayer and then milling a gap layer and the notching layer, employing asecond pole tip as a mask, until side walls of the second pole tip, thegap layer and the notching layer are contiguous.

2. Description of the Related Art

A write head is typically combined with a magnetoresistive (MR) readhead to form a merged MR head, certain elements of which are exposed atan air bearing surface (ABS). The write head comprises first and secondpole pieces connected at a back gap that is recessed from the ABS. Thefirst and second pole pieces have first and second pole tips,respectively, which terminate at the ABS. An insulation stack, whichcomprises a plurality of insulation layers, is sandwiched between thefirst and second pole pieces, and a coil layer is embedded in theinsulation stack. A processing circuit is connected to the coil layerfor conducting write current through the coil layer which, in turn,induces write fields in the first and second pole pieces. A non-magneticgap layer is sandwiched between the first and second pole tips. Writefields of the first and second pole tips at the ABS fringe across thegap layer. In a magnetic disk drive, a magnetic disk is rotated adjacentto, and a short distance (fly height) from, the ABS so that the writefields magnetize the disk along circular tracks. The written circulartracks then contain information in the form of magnetized segments withfields detectable by the MR read head.

An MR read head includes an MR sensor sandwiched between first andsecond non-magnetic gap layers, and located at the ABS. The first andsecond gap layers and the MR sensor are sandwiched between first andsecond shield layers. In a merged MR head, the second shield layer andthe first pole piece are a common layer. The MR sensor detects magneticfields from the circular tracks of the rotating disk by a change inresistance that corresponds to the strength of the fields. A sensecurrent is conducted through the MR sensor, where changes in resistancecause voltage changes that are received by the processing circuitry asreadback signals.

One or more merged MR heads may be employed in a magnetic disk drive forreading and writing information on circular tracks of a rotating disk. Amerged MR head is mounted on a slider that is carried on a suspension.The suspension is mounted to an actuator which rotates the magnetic headto locations corresponding to desired tracks. As the disk rotates, anair layer (an "air bearing") is generated between the rotating disk andan air bearing surface (ABS) of the slider. A force of the air bearingagainst the air bearing surface is opposed by an opposite loading forceof the suspension, causing the magnetic head to be suspended a slightdistance (flying height) from the surface of the disk. Flying heightsare typically on the order of about 0.05 μm.

The second pole, along with its second pole tip, is frame-plated on topof the gap layer. After depositing a seed layer on the gap layer, aphotoresist layer is spun on the seed layer, imaged with light, anddeveloped to provide an opening surrounded by a resist wall for platingthe second pole piece and second pole tip. To produce a second pole tipwith a narrow track width, the photoresist layer has to becorrespondingly thin. This relationship, referred to as the "aspectratio", is the ratio of the thickness of the photoresist in the pole tipregion to the track width of the second pole tip. Preferably, the aspectratio should be on the order of three. In other words, for a track widthof 1 μm, the thickness of the photoresist in the pole tip region shouldbe about 3 μm. If the photoresist is thicker than this, the side wallsof the second pole tip, especially at the base, will not be well-formeddue to scattering of light as it penetrates the photoresist during theimaging step.

Once the second pole tip is formed, it is desirable to notch the firstpole piece opposite the first and second bottom corners of the secondpole tip. Notching the first pole piece minimizes side writing in trackswritten on the magnetic disk. As is known, when the tracks areoverwritten by side writing the track density of the magnetic disk isreduced. When the first pole piece is notched, it has first and secondside walls that are aligned with first and second side walls of thesecond pole tip, so that the first pole piece and the second pole tiphave the same track width at the ABS. This minimizes fringing ofmagnetic fields from the second pole tip laterally beyond the trackwidth (side writing) to a wide expanse of the first pole piece.

A prior art process for notching the first pole piece entails ion beammilling the gap layer and the first pole piece, employing the secondpole tip as a mask. According to this prior art process (typified inU.S. Pat. No. 5,452,164 and U.S. Pat. No. 5,438,747), the gap layer istypically alumina, and the first and second pole pieces and pole tipsare typically Permalloy (NiFe). Alumina mills more slowly thanPermalloy; thus the top of second pole tip and a top surface of thefirst pole piece are milled more quickly than the gap layer. Further,during ion milling, there is significant redeposition of alumina onsurfaces of the workpiece. The milling ion beam is typically directed atan angle with respect to a normal to the layers, in order that millingand clean-up be done simultaneously.

Notching the first pole piece is very time consuming due, in part, toshadowing of the notch sites by the angled milling and by the profile ofthe second pole tip, as the wafer supporting the magnetic head isrotated. The length of milling time is due more, however, to the largelateral expanse of the first pole piece. Since the top and side walls ofthe second pole tip are also milled while the first pole piece is beingnotched, the second pole tip has to be formed with extra thickness andwidth so that, after notching is completed, the second pole tip is atits target height and target track width. Unfortunately, because of thelong time required for notching it is difficult to meet the targetswithin acceptable tolerances. This has lowered manufacturing yield.Also, the extra height of the initially formed second pole tip increasesthe aspect ratio and reduces the line width of the second pole tip.

In order to minimize overmilling of the first pole piece, anotherprocess removes the gap layer, except for a desired portion between thefirst and second pole tips, by a wet etchant. After the unwantedportions of the gap layer are removed, the first pole piece is ionmilled, employing the second pole tip as a mask. This process eliminatessignificant redeposition of the alumina. A problem with this process,however, is that the etching undercuts the gap layer under the base ofthe second pole tip, which is a critical area for the transfer of fieldsignals. The undercut regions provide spaces where Permalloy can beredeposited during subsequent ion milling of the first pole piece, orother foreign material can be redeposited upon subsequent milling andclean-up steps. Further, if the track width of the second pole tip is inthe order of 1 μm, the etchant may release the second pole tip from thegap layer, thus ruining the head.

SUMMARY OF THE INVENTION

We have discovered that construction of a notching layer on a typicalfirst pole piece layer with first and second corners adjacent the firstand second side walls of the second pole tip will reduce the millingtime required for notching. We construct the first pole piece layer witha wide lateral expanse, and the notching layer on the first pole piecelayer with a narrow lateral expanse. We prefer the width of the notchinglayer to be 0.5 μm to 2.0 μm wider than the target track width of thesecond pole tip. With this arrangement, the notching layer has first andsecond side walls which project 0.25 to 1.0 μm laterally beyond thefirst and second side walls, respectively, of the second pole tip. Thethickness of the notching layer is, preferably, between 0.2 μm to 1.0μm. Accordingly, full notching of the notching layer can be achieved bymilling a small corner in a range of 0.25 μm by 0.2 μm to 1.0 μby 1.0μm, as seen in an ABS view. The gap layer is formed on the notchinglayer, followed by formation of the second pole tip on the gap layer.Milling at an angle is then employed to penetrate the gap layer andnotch the notching layer. In comparison to the prior art where a largelateral expanse of the first pole piece is milled to achieve notching,milling the small corner of the notching layer requires a very shortmilling time. This results in less consumption of the second pole tip,so that better control of a final track width can be accomplished. Also,since there is less consumption of the top of the second pole tip, theaspect ratio of the photoresist employed to construct the second poletip is lessened so as to enhance the line width of the second pole tip.Further, there is less redeposited material to clean up after themilling cycle. All of these factors reduce the process time and increasemanufacturing throughput.

Another advantage of the present invention is that the milling thatremoves a second pole tip seed layer can be continued to performnotching. This still further lessens the process time by obviating anynecessity of making a separate set up. Still another advantage is thatthe first pole piece layer and the notching layer of the first polepiece can be constructed of different materials, with different magneticmoments. Still a further advantage of the present invention is that thefirst pole piece can be notched on only one side, which provides thesame benefits for servoing that are afforded by a double-notched firstpole piece. A single-notched first pole piece can be formed by employingthe above method, with the exception that the notching layer is given awide expanse on the side that is not to be notched. Since the corner onthe opposite side is quickly milled, there is very little notching ofthe wide expanse. It should be noted that single-side notching will alsoresult in less redeposition of milled material.

Process time can still further be reduced with the single-side notchingembodiment by forming the second pole piece with an asymmetrical flareand a matching notching layer. The second pole piece flares outlaterally in first and second directions, from a recessed end of thesecond pole tip, to a recessed yoke portion of the second pole piece.The commencement of the flare is referred to as the flare point. We havediscovered that by keeping a normal flare point on the side of the wideexpanse, where the notching layer is not to be notched, and a flarepoint recessed from the normal flare point, on the side of the narrowexpanse where the notching layer is to be notched, there is lessshadowing of the notch site during the milling cycle. The notching layeris configured similarly to the second pole piece, with an asymmetricalflare portion and a border extension from the second pole piece. Withthis arrangement the second pole piece and the notching layer arefurther back on the side where notching is to take place, lengtheningthe time that the angled milling beam strikes the notching site duringrotation of the wafer supporting the partially completed magnetic head.

An object of the present invention is to provide a method of notching afirst pole piece with less processing time.

Another object is to provide a method of notching a first pole piecewith more control of the target track width of the second pole tip.

A further object is to provide a method of notching a first pole piecewith less consumption of the second pole tip and less redeposition tocleanup after notching the first pole piece.

Still another object is to provide a method wherein single side notchingcan be performed.

Still a further object is to provide a first pole piece of a magnetichead with a notching layer which is only partially notched.

Yet another object is to provide a first pole piece of a magnetic headthat has different materials with different magnetic moments.

Other objects and attendant advantages of the invention will beappreciated upon reading the following description taken together withthe drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a planar view of an exemplary magnetic disk drive;

FIG. 2 is an end view of a slider with a magnetic head of the disk driveas seen in plane II--II;

FIG. 3 is an elevation view of the magnetic disk drive wherein multipledisks and magnetic heads are employed;

FIG. 4 is an isometric illustration of an exemplary suspension systemfor supporting the slider and magnetic head;

FIG. 5 is a partial elevation view of the slider and magnetic head asseen in plane V--V of FIG. 2;

FIG. 6 is a top view of the second pole piece and coil layer, a portionof which is shown in FIG. 5, with all insulation material removed;

FIG. 7 is a partial ABS view of the slider taken along plane VII--VII ofFIG. 5 to show the read and write elements of the magnetic head;

FIG. 8 is an ABS of a prior art head prior to notching the first polepiece;

FIG. 9 is an ABS view of the prior art head after the first pole pieceis formed with notches by milling;

FIG. 10 is an ABS view of an initial step of the present invention wherea notching layer (PIN) is formed for notching the first pole piece;

FIG. 11 is a view taken along plane XI--XI of FIG. 10;

FIG. 12 is an ABS view of the next step in the present invention where aP1 seed layer is removed;

FIG. 13 is an ABS view of the present invention after forming a gaplayer at the ABS;

FIG. 14 is an ABS view of the method wherein the second pole piece,including a second pole tip, is frame plated on the gap layer;

FIG. 15 is a view taken along plane XV--XV of FIG. 14;

FIG. 16 is an ABS view of a step of chemically etching unwanted secondpole piece material in the field;

FIG. 17 is an ABS view of the present invention showing the notchinglayer being partially notched by ion milling;

FIG. 18 is an ABS view showing the notching layer fully notched by ionmilling;

FIG. 19 is an ABS view similar to FIG. 18 except the first pole piecelayer is also partially notched;

FIG. 20 is similar to FIG. 17 except an overcoat layer has been formed;

FIG. 21 is the first step of another embodiment of the present inventionwherein a notching layer (PIN) is formed;

FIG. 22 is a view taken along plane XXII--XXII of FIG. 21 showing afirst aspect of the second embodiment shown in FIG. 21, with the secondpole piece shown in phantom;

FIG. 23 is a view taken along plane XXIII--XXIII of FIG. 21 showing asecond aspect of the second embodiment of the invention shown in FIG. 21with the second pole piece shown in phantom;

FIG. 24 is an ABS view of a second step in the second embodiment whereina P1 seed layer is removed;

FIG. 25 is an ABS view showing the formation of a gap layer;

FIG. 26 is an ABS view showing frame plating the second pole tip on thegap layer;

FIG. 27 is an ABS view showing chemically etching unwanted second polepiece material in the field;

FIG. 28 is an ABS view of the second embodiment of the invention afternotching the PIN by ion milling;

FIG. 29 is an alternative embodiment similar to FIG. 28 except thebottom layer of the first pole piece has also been slightly notched byion milling;

FIG. 30 is an ABS view of the embodiment shown in FIG. 28 after formingan overcoat.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, wherein like reference numerals designatelike or similar parts throughout the several views, there is illustratedin FIGS. 1-3 a magnetic disk drive 30. The drive 30 includes a spindle32 that supports and rotates a magnetic disk 34. The spindle 32 isrotated by a motor 36 that, in turn, is controlled by a motor controller38. A horizontal combined magnetic head 40 for reading and recording ismounted on a slider 42. The slider 42 is supported by a suspension 44and actuator arm 46. A plurality of disks, sliders and suspensions maybe employed in a large capacity direct access storage device (DASD), asshown in FIG. 3. The suspension 44 and actuator arm 46 position theslider 42 to locate the magnetic head 40 in a transducing relationshipwith a surface of the magnetic disk 34. When the disk 34 is rotated bythe motor 36, the slider is supported on a thin (typically, 0.05 μm)cushion of air (air bearing) between the disk and an air bearing surface(ABS) 48.

The magnetic head 40 may be employed for writing information to multiplecircular tracks on the surface of the disk 34, as well as for readinginformation therefrom. Processing circuitry 50 exchanges signalsrepresenting such information with the head 40, provides motor drivesignals, and also provides control signals for moving the slider 42 tovarious tracks. In FIGS. 1 and 4 the slider 42 is shown mounted to ahead gimbal assembly (HGA) 52 that is mounted to the suspension 44. Allof the above components are supported on a base 53.

FIG. 5 is a side cross-sectional elevation view of a mergedmagnetoresistive (MR) head 40, with a write head portion 54 and a readhead portion 56. The read head portion includes an MR sensor 58. The MRsensor 58 is sandwiched between first and second gap layers 60 and 62that are, in turn, sandwiched between first and second shield layers 64and 66. In response to external magnetic fields, the resistance of theMR sensor 58 changes. A sense current conducted through the sensorcauses these resistance changes to be manifested as potential changes,which are processed by the processing circuitry 50 shown in FIG. 3.

The write head portion 54 of the head includes a coil layer 68sandwiched between first and second insulation layers 70 and 72. A thirdinsulation layer 74 may be employed for planarizing the head toeliminate ripples in the second insulation layer caused by the coillayer 68. The first, second and third insulation layers are referred toas an "insulation stack". The coil layer 68, and the first, second andthird insulation layers 70, 72 and 74, are sandwiched between first andsecond pole piece layers 76 and 78. The first and second pole piecelayers 76 and 78 are magnetically coupled at a back gap 80, and havefirst and second pole tips 82 and 84 that are separated by anon-magnetic gap layer 86 at the ABS. As shown in FIGS. 2 and 4, firstand second solder connections 88 and 90 connect leads (not shown) fromthe MR sensor 58 to leads 96 and 98 on the suspension 44; third andfourth solder connections 100 and 102 connect leads 104 and 106 from thecoil 68 (see FIG. 6) to leads 108 and 110 on the suspension.

FIG. 8 shows an ABS view of a prior art merged magnetic head, in whichthe second shield of the read head and the first pole piece of the writehead are a common layer 66/76. The gap layer 120 has been formed on thefirst pole piece layer 66/76, followed by frame plating a second poletip 122 on the gap layer 120. The second pole tip 122 is a front portionof the second pole piece. The second pole tip is bounded by a top 124,first and second side walls 126 and 128, and a base 130. The targettrack width (TW) is shown in FIG. 8. Since the first pole piece will benotched by ion milling, the second pole tip 122 is larger than a targetsize track width (TW) of the second pole tip, so as to allow forconsumption of the second pole tip during a subsequent milling cycle.Accordingly, before milling, the first and second side walls 126 and 128extend beyond the track width, and the top 124 is higher than the targetheight. The dimensions of these sacrificial portions is referred to inthe art as windage.

In FIG. 9 ion milling is employed to mill through the gap layer to forma write gap 130 with first and second side walls 132 and 134, and tomill notches into the first pole piece 66/76 with first and second sidewalls 136 and 138. After milling, the first side walls 126, 132 and 136are contiguous, and the second side walls 128, 134 and 138 arecontiguous. This notching improves the transfer of flux between thesecond pole tip 122 and the first pole piece 66/76, since the flux willtransfer to the pedestal portion of the first pole piece instead of thelarger expanse thereof. This reduces side writing by the write head. Themilling is at an angle to a normal to the layers 66/76 and 64 in orderto minimize redeposition of the milled material. It should be understoodthat the partially completed magnetic head in FIG. 9 rests upon asubstrate (not shown) that is rotated during the milling cycle. Thesecond pole tip is employed as a mask for forming the write gap 130 andnotching the first pole piece at 136 and 138. It can be seen that thiscauses shadowing at the notching sites 136 and 138 during approximately180° of the rotation, due to the angle of the milling. This shadowingincreases the processing time required to form the notches in the firstpole piece. It should be noted that the downward sloping portions of thefirst pole piece layer 62 in FIG. 9 are formed due to the shadowing bythe second pole tip 122.

After milling, the second pole tip 122 has been reduced in size. Withthe prior art method it is very difficult to reduce the second pole tip122 to the target track width and the target height because of thesignificant time required for milling the large lateral expanse of thefirst pole tip 66/76. Milling of flat surfaces is very time-consuming ascompared to side walls. Further, the top 124 in FIG. 8 requires extraheight because of the long time required for milling. This extra heightincreases the aspect ratio (ratio between height of resist employed toframe plate the second pole tip 122 and the target track width), whichreduces the line width of the second pole tip. Prior art methods ofnotching the first pole piece discussed in commonly assigned U.S. Pat.Nos. 5,438,747 and 5,452,164 indicate a strong-felt need to reduce thetime required to notch the first pole piece of a write head. Theinvention advantageously reduces this notching time.

FIGS. 10-20 illustrate a first embodiment of the present invention,which significantly decreases the milling time required to notch thefirst pole piece. In the present invention, the first pole piececomprises two layers, namely a first pole piece layer 200, which may beidentical to the layer 66/76 in FIG. 8, and a notching layer 202 on topof the first pole piece layer 200. The notching 202 is also referred toas a first pole piece notch (PIN). The notching layer 202 has a top 204,and first and second side walls 206 and 208. The side walls 206 and 208extend beyond the target track width (TW) by an amount that is kept assmall as possible in order to reduce the subsequent milling cycle. Apreferred range for the extension of each side wall 206 and 208 beyondthe target track width is 0.10 μm to 1 μm. The thickness of the notchinglayer may be 0.10 μm to 1 μm, depending upon the notching requirement.Accordingly, the corners of the notching layer to be moved during thenotching cycle are the small portions shown outside of the target trackwidth. The area of each corner, as seen in ABS view, would be in therange from 0.01 μm to 1.00 μm. It can be seen that the amount of millingtime required to completely remove these corners is significantly lessthan that required to mill the large lateral expanses of the first polepiece layer 66/76 shown in FIG. 9.

The first step in the present invention is to frame plate the notchinglayer 204, as shown in FIG. 10. It should be noted that the MR sensor 58is centered between the target track width, and has a track widthslightly less than the track width of the write head, so as to satisfythe requirement of "write wide and read narrow". FIG. 11 shows a planview of the notching layer 202; the second pole piece is shown inphantom at 210, since it hasn't yet been formed.

In FIG. 12 a seed layer (not shown), employed for constructing the firstpole piece layer 200, is removed by any suitable means such as ionmilling. This ion milling slightly rounds the top corners of thenotching layer 202, as shown in FIG. 12. The next step is to deposit afull film gap layer 205, as shown in FIG. 13. The thickness of the gaplayer may be on the order of 0.2 μm. This covers the top 204 and thefirst and second side walls 206 and 208 of the notching layer, as wellas the top of the first pole piece layer 200 in the field. The seedlayer can be removed by either R.F. sputter etching or ion milling.

The next step is to frame plate the second pole piece, which includes asecond pole tip 210, on top of the gap layer 205 above the notchinglayer 202. The second pole tip 210 is formed with extra thickness andextra width, as shown in FIG. 14, to allow for windage, namelyconsumption of the second pole tip by processing steps. An extrathickness of 0.5 μm to 1.0 μm has been found to be satisfactory to allowfor windage. The second pole tip 210 in FIG. 14 is bounded by a top 212,first and second side walls 214 and 216, and a base 218. The side walls214 and 216 are milled by the subsequent milling step until they alignwith the target track width (TW). As shown in FIG. 16, the top of thesecond pole tip is covered with a resist layer 220 and field regions ofthe second pole piece are removed by chemical etching.

In FIG. 17 the resist layer 220 has been removed, and ion milling isused to notch the notching layer 202. Ion milling is done at an angle toa normal to the top surfaces of the layers 64 and 200. A preferablerange for this angle is 10° to 55° so as to ensure good milling andcleanup of any redeposited material. The milling first mills through thegap layer 205 of FIG. 16 to form a write gap layer 222, with first andsecond side walls 224 and 226. FIG. 17 shows one embodiment of thepresent invention wherein the notching layer 202 is partially notchedwith first and second side walls 228 and 230. In this embodiment, thenotching layer 202 has third and fourth side walls 232 and 233, whichare located laterally outwardly from the first and second side walls 228and 230, respectively. A very short milling cycle is required to millthe notches at 228 and 230, compared to milling the large lateralexpanse of the first pole piece layer 200. One of the advantages of thepresent invention is that the ion milling cycle shown in FIG. 17 ispreferably a continuation of an ion milling cycle to remove a secondpole tip seed layer employed to construct the second pole piece andsecond pole tip 210. Accordingly, the milling in FIG. 17 does notrequire a separate setup from the normal processing of the write head.Since less processing time is required to mill the notches at 228 and230, the track width of the second pole tip 210, as defined by the sidewalls 214 and 216, at the base 218 can more nearly match the targettrack width (TW) than that obtained by the prior art.

FIG. 18 is a second embodiment of the invention wherein the ion millingis employed to simply make first and second side walls 234 and 235 ofthe notching layer contiguous with the first and second side walls 224and 226 of the gap layer and the first and second side walls 214 and 216of the second pole tip layer. FIG. 19 illustrates still a furtherembodiment of the invention, wherein the ion milling cycle is employedto slightly notch the first pole piece layer 200 of the first pole piecewith first and second side walls 236 and 238. Field regions 240 and 242of the first pole piece layer 200 of the first pole piece in FIG. 19slope slightly downwardly from the notches at 236 and 238 because of thelonger milling cycle and shadowing by the second pole tip 210. Thepreferred embodiment is shown in FIG. 17. In all embodiments, millingcontinues until the first side walls are contiguous and the second sidewalls are contiguous of each of the second pole tip 210, the gap layer222 and the notching layer 202. In the FIG. 19 embodiment, the firstside walls 214, 224, 234 and 236 are contiguous and the second sidewalls 216, 226, 235 and 238 are contiguous.

In all three embodiments, the second pole tip is frame plated in FIG. 14with sufficient thickness and width, so that, after the termination ofthe milling cycle, the track width of the second pole tip 210 in FIGS.17, 18 and 19 is aligned with the target track width (TW). In all threeembodiments, very small corners of the notching layer 202 have beenremoved by the milling, which requires significantly less time thanmilling the large expanse of the first pole piece layer 200 in order toachieve notching. After completion of the notching, an overcoat layer240 is formed, as shown in FIG. 20. This is shown for the preferredembodiment, which was constructed in FIG. 17.

FIGS. 21-30 illustrate another embodiment of the invention whichimplements single side notching of the first pole piece. In FIG. 21, anotching layer 250 (PIN) is frame plated on the first pole piece layer200 of the first pole piece. The first pole piece includes the firstpole piece layer 200 and the notching layer 250. The notching layer 250has a top 252 and a first side wall 254, which is the same as the sidewall 206 shown in FIG. 10. The notching layer 250 differs from theprevious embodiment in that the top 252 has a large expanse, which maycoincide with the lateral expanse of the first pole piece layer 200 asit extends away from the first side wall 254. Accordingly, the notchinglayer 250 has only one corner at the side wall 254, milled in asubsequent step for notching purposes.

Two embodiments of the planar shape of the notching layer 250 are shownin FIGS. 22 and 23. In FIG. 22, the second pole piece is shown inphantom at 260, with a pole tip region 262, a flare region 264 and ayoke region 266, the commencement of the flare region 264 being shown atflare points 268 and 270. In this embodiment the flare point 268,located on the side where the notching layer 250 is to be notched, isrecessed farther into the head than the flare point 270. Accordingly,the notched layer 250 is provided with an inside corner 272 that isadjacent to the flare point 268, and that matches the flare 264 back tothe yoke region 266. On the other side of the pole tip region 262, wherethe flare point 270 is located, notching will not be implemented, andthe notching layer 250 provides a wide lateral expanse extending fromthe pole tip region 262. In this embodiment, the notching layer 250 isframe plated with a planar shape, as shown in FIG. 22.

Another embodiment of the notching layer 250 is shown in FIG. 23. Inthis embodiment, the second pole piece 274 has a pole tip region 276, aflare region 278 and a yoke region 280. The flare region 278 commencesat flare points 282 and 284. In this embodiment, the notching layer 250has an inside corner 286 that is adjacent the flare point 282 and thatextends along just the outside of the flare region 278 and the yokeregion 280. The notching layer 250 on the opposite side of the pole tipregion 276 has a large lateral expanse, as does the notching layer inFIG. 22.

The difference between FIGS. 22 and 23 is that the flare in FIG. 22 isasymmetrical, while the flare in FIG. 23 is symmetrical. The embodimentshown in FIG. 22 has an advantage from a processing standpoint, in thatthe second pole piece 260 on the side of the notched layer to be notchedis recessed further into the head, so as to minimize shadowing by thesecond pole piece when the notched layer is milled, which will bedescribed in more detail hereinafter. This advantage has to be balancedwith the magnetics of the head, as compared to the typical symmetricalflare region 286 shown in FIG. 23. At this point in the process, thesecond pole piece 266 in FIG. 22 and the second pole piece at 280 inFIG. 23 have not been formed.

In FIG. 24, the first pole piece seed layer is removed, which causes aslight rounding of the upper corner of the notched layer 250. Next, agap layer 290 is deposited along with a first insulation layer (notshown), a coil layer (not shown), a second insulation layer (not shown),and a third insulation layer (not shown). The first insulation layer,the coil layer, the second insulation layer, and the third insulationlayer can be seen in FIG. 5 at 70, 68, 72 and 74 respectively. The gaplayer 290 is a full film layer that covers the entire top 252 of thenotching layer, the side 254 of the notching layer, and the remaininglateral expanse of the first pole piece layer.

The next step is to frame plate the second pole piece, along with asecond pole tip 292, as shown in FIG. 26. The second pole tip 292 isbounded by a top 294, first and second side walls 296 and 298, and abase 300. As stated hereinabove, the thickness and width of the secondpole tip 292 is enlarged to account for erosion by processing steps,including the subsequent milling step for notching the notching layer250. In FIG. 27 a resist layer 302 is formed on top of the second poletip, and second pole piece material located in the field is removed bychemical etching. In FIG. 28 ion milling is implemented at an angle to anormal to the planes of the layers 64 and 200, this angle beingpreferably 10° to 55°, as discussed hereinabove. This milling reducesthe gap layer 290 in FIG. 27 to form a write gap layer 304 with firstand second side walls 306 and 308. The milling continues until the firstside walls 296, 306 and 254 are contiguous. This milling causes a veryslight notching in the large lateral expanse of the notching layer 250,forming a very small side wall 310. For all practical purposes, thefirst pole piece has been provided with a single notch at 254. In FIG.29, a longer milling cycle is employed to notch into the first polepiece layer 200 to form a first side wall 314. In this embodiment themilling cycle is employed until the first side walls 296, 306, 254 and314 are contiguous. The notching layer on the other side of the pole tipwould be slightly notched, as shown at 316. The preferred embodiment isshown in FIG. 28, since less milling time is required, which embodimentis shown formed with an overcoat in FIG. 30. It should be understoodthat the notching layer 250 could optionally be partially notched, asshown in FIG. 17, if desired.

Clearly, other embodiments and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. Therefore, this invention is to be limited only by thefollowing claims, which include all such embodiments and modificationswhen viewed in conjunction with the above specification and accompanyingdrawings.

We claim:
 1. A method of making a write head that has an air bearingsurface (ABS) and a notched first pole piece at the ABS, the notchedfirst pole piece conforming to a predetermined track width of a secondpole tip layer, the method comprising:forming a first pole piece layerperpendicular to the ABS; forming a notching layer on the first polepiece layer with a lateral width at the ABS that is narrower than alateral width of the first pole piece layer at the ABS, the notchinglayer having at least a first side wall laterally spaced a predetermineddistance in a first direction laterally from said track width; forming agap layer on the notching layer; forming a second pole tip layer on thegap layer with first and second side walls and a lateral width that islarger than said track width; and using the second pole tip layer as amask, milling a portion of the gap layer and the first side wall of thenotching layer not under the second pole tip until the gap layer has afirst side wall and until the first side walls of the second pole tiplayer, the gap layer and at least a portion of the first side wall ofthe notching layer are aligned with respect to one another.
 2. Themethod as claimed in claim 1, further including:forming the layers on asubstrate; the forming of the first pole piece layer, the notchinglayer, the gap layer and the second pole tip layer forming each of theselayers with a top flat surface; said milling being at an angle between10° to 55° to a normal to the top flat surfaces of said layers; androtating the substrate while milling.
 3. The method as claimed in claim1, further including:said milling also milling the first pole piecelayer with a first side wall which is contiguous with said first sidewall of the notching layer.
 4. The method as claimed in claim 1, whereinthe notching layer is formed with a different magnetic moment materialthan a magnetic moment material of the first pole piece layer.
 5. Themethod as claimed in claim 1, wherein said predetermined distance is ina range of 0.10 μm to 1.0 μm.
 6. The method as claimed in claim 1,further including:prior to forming the second pole tip layer, forming aseed layer on the gap layer, and then forming the second pole tip layeron the seed layer; and milling a portion of the seed layer not under thesecond pole tip layer; and employing a same milling cycle for firstmilling said portion of the seed layer and then milling said portion ofthe gap layer and the first side wall of the notching layer.
 7. Themethod as claimed in claim 1, further including:forming the notchinglayer with a second side wall laterally spaced said predetermineddistance in a second direction laterally from said track width; and saidmilling also milling said portion of the gap layer and the second sidewall of the notching layer not under the second pole tip until the gaplayer has a second side wall and until the second side walls of thesecond pole tip layer, the gap layer and at least a portion of thesecond side wall of the notching layer are contiguous.
 8. The method ofclaim 7, wherein the combined magnetic head further includes a readhead, wherein making the read head comprises:before forming the firstpole piece layer of the first pole piece, forming a first shield layer;forming a first gap layer on the first shield layer; forming amagnetoresistive (MR) sensor with first and second lead layers on thefirst gap layer, the MR sensor being centered with respect to said trackwidth at the ABS; forming a second gap layer on the MR sensor, the firstand second lead layers and the first gap layer; and said forming of thefirst pole piece layer forming the first pole piece layer on the secondgap layer.
 9. The method as claimed in claim 7, wherein saidpredetermined distance is formed in a range of 0.1 μm to 1.0 μm.
 10. Themethod as claimed in claim 9, wherein the notching layer is formed witha thickness of 0.1 μm to 1.0 μm.
 11. The method as claimed in claim 10,wherein the track width is formed 1 μm or less.
 12. The method asclaimed in claim 11, further including:prior to forming the second poletip layer, forming a seed layer on the gap layer, and then forming thesecond pole tip layer on the seed layer; milling a portion of the seedlayer not under the second pole tip layer; and employing a same millingcycle for first milling said portion of the seed layer and then millingsaid portion of the gap layer and the first side wall of the notchinglayer.
 13. The method as claimed in claim 12, further including:formingthe layers on a substrate; the forming of the first pole piece layer,the notching layer, the gap layer and the second pole tip layer formingeach of these layers with a top flat surface; said milling being at anangle between 10° to 55° to a normal to the top flat surfaces of saidlayers; and rotating the substrate while milling.
 14. The method asclaimed in claim 13, further including:said milling also milling thefirst pole piece layer with first and second side walls that arecontiguous with the first and second side walls, respectively, of thenotching layer.
 15. The method as claimed in claim 13, wherein thenotching layer is formed with a different magnetic moment material thana magnetic moment material of the first pole piece layer.
 16. The methodas claimed in claim 15, further including:forming the first pole piecelayer of substantially Ni₈₀ Fe₂₀ material, and forming the notchinglayer of substantially Ni₄₅ Fe₅₅ material.
 17. The method as claimed inclaim 15, further including:forming the first pole piece layer ofsubstantially Ni₄₅ Fe₅₅ material and forming the notching layer ofsubstantially Ni₈₀ Fe₂₀ material.
 18. The method as claimed in claim 13,further including:before forming the second pole tip layer:forming afirst insulation layer on the notching layer; forming a coil layer onthe first insulation layer; and forming at least a second insulationlayer on the coil layer; and said forming of the second pole tip layeralso forming the second pole piece layer on the second insulation layer.19. A method of making a write head that has an air bearing surface(ABS) and a notched first pole piece at the ABS, the notched first polepiece conforming to a predetermined track width of a second pole tiplayer, the method comprising:forming a first pole piece layerperpendicular to the ABS; forming a notching layer on the first polepiece layer with a lateral width at the ABS that is narrower than alateral width of the first pole piece layer at the ABS, the notchinglayer having at least a first side wall laterally spaced a predetermineddistance in a first direction laterally from said track width; forming agap layer on the notching layer; forming a second pole tip layer on thegap layer with first and second side walls and a lateral width that islarger than said track width; using the second pole tip layer as a mask,milling a portion of the gap layer and the first side wall of thenotching layer not under the second pole tip until the gap layer has afirst side wall and until the first side walls of the second pole tiplayer, the gap layer and at least a portion of the first side wall ofthe notching layer are contiguous; the forming of the notching layerforming the notching layer with a flare portion, the flare portionhaving first and second sides that extend in said first and seconddirections away from the second pole tip layer, the first and secondsides of the flare being recessed from the ABS and the recession of thefirst side being more than the recession of the second side; the formingof the second pole tip layer also forming a second pole piece layer, thesecond pole piece layer having a flare portion, the flare portion havingfirst and second sides that extend in said first and second directionsaway from the second pole tip layer, the first and second sides of theflare being recessed from the ABS and the recession of the first sidebeing more than the recession of the second side; and the notching layerhaving a second side wall located a distance greater than saidpredetermined distance from the track width in said second direction.20. The method of claim 19, wherein the combined magnetic head furtherincludes a read head, wherein making of the read head comprises:beforeforming the first pole piece layer of the first pole piece, forming afirst shield layer; forming a first gap layer on the first shield layer;forming a magnetoresistive (MR) sensor with first and second lead layerson the first gap layer, the MR sensor being centered with respect tosaid track width at the ABS; and forming a second gap layer on the MRsensor, the first and second lead layers and the first gap layer; andsaid forming of the first pole piece layer forming the first pole piecelayer on the second gap layer.
 21. The method as claimed in claim 19,wherein said predetermined distance is in a range of 0.1 μm to 1.0 μm.22. The method as claimed in claim 21, wherein the notching layer isformed with a thickness of 0.1 μm to 1.0 μm.
 23. The method as claimedin claim 22, wherein the track width is formed 1 μm or less.
 24. Themethod as claimed in claim 23, further including:prior to forming thesecond pole tip layer, forming a seed layer on the gap layer, and thenforming the second pole tip layer on the seed layer; and milling aportion of the seed layer not under the second pole tip layer; andemploying a same milling cycle for first milling said portion of theseed layer and then milling said portion of the gap layer and the firstside wall of the notching layer.
 25. The method as claimed in claim 24,further including:forming the layers on a substrate; the forming of thefirst pole piece layer, the notching layer, the gap layer and the secondpole tip layer forming each of these layers with a top flat surface;said milling being at an angle between 10° to 55° to a normal to the topflat surfaces of said layers; and rotating the substrate while milling.26. The method as claimed in claim 24, further including:said millingalso milling the first pole piece layer with a first side wall which iscontiguous with said first side wall of the notching layer.
 27. Themethod as claimed in claim 24, wherein the notching layer is formed witha different magnetic moment material than a magnetic moment material ofthe first pole piece layer.
 28. The method as claimed in claim 27,further including:forming the first pole piece layer of substantiallyNi₈₀ Fe₂₀ material, and forming the notching layer of substantially Ni₄₅Fe₅₅ material.
 29. The method as claimed in claim 27, furtherincluding:forming the first pole piece layer of substantially Ni₄₅ Fe₅₅material, and forming the notching layer of substantially Ni₈₀ Fe₂₀material.
 30. The method as claimed in claim 24, furtherincluding:before forming the second pole tip layer:forming a firstinsulation layer on the notching layer; forming a coil layer on thefirst insulation layer; and forming at least a second insulation layeron the coil layer; and said forming of the second pole tip layer alsoforming the second pole piece layer on the second insulation layer. 31.A method of making a partially completed write head that has an airbearing surface (ABS) site and a second pole tip layer that has a trackwidth at the ABS site comprising:forming a first pole piece layer with atrack width site that is in alignment with a second pole tip layer trackwidth site that corresponds to said track width of the second pole tiplayer and with top and bottom surfaces and first and second side edgesthat are outboard of the track width site of the first pole piece layer;forming a notching layer on the top surface of the first pole piecelayer with a track width site that is in alignment with said second poletip layer track width site and with top and bottom surfaces and firstand second side edges that are inboard of the first and second sideedges of the first pole piece layer but outboard of the track width siteof the notching layer; forming a write gap layer on the notching layerand the first pole piece layer that has a track width site in alignmentwith the second pole tip layer track width site; forming a partiallyformed second pole tip layer on the write gap layer with a track widthsite in alignment with the second pole tip layer track width site andwith top and bottom surfaces and first and second side edges that areinboard of the first and second side edges of the notching layer butoutboard of the track width site of the partially formed second pole tiplayer; while employing the partially formed second pole tip layer as amask, ion milling the partially formed second pole tip layer, portionsof the write gap layer and portions of the notching layer until thepartially completed second pole tip layer is formed into said secondpole tip layer with first and second side edges that coincide with anddefine said track width.
 32. A method as claimed in claim 31including:each of the first pole piece layer and the notching layerbeing formed with a ferromagnetic material with a magnetic moment; andthe magnetic moment of the notching layer being greater than themagnetic moment of the first pole piece layer.
 33. A method as claimedin claim 32 wherein the first pole piece layer is formed ofsubstantially Ni₈₀ Fe₂₀ and the notching layer is formed ofsubstantially Ni₄₅ Fe₅₅.
 34. A method as claimed in claim 31 wherein,before ion milling, each of the side edges of the notching layer extends0.10 μm to 1.0 μm beyond the track width site of the notching layer. 35.A method as claimed in claim 31 including:the forming of the notchinglayer forming the first and second side edges and the top surface of thenotching layer with first and second corners respectively; and said ionmilling milling away said first and second corners.
 36. A method asclaimed in claim 31 wherein, during ion milling, the write gap layer ismilled with first and second side edges that are contiguous with thefirst and second side edges respectively of the second pole tip layerand the notching layer is milled with first and second side edges thatare contiguous with the milled first and second side edges respectivelyof the write gap layer.
 37. A method as claimed in claim 36 wherein,before ion milling, each of the side edges of the notching layer extends0.10 μm to 1.0 μm beyond the track width site of the notching layer. 38.A method as claimed in claim 37 including:the forming of the notchinglayer forming the first and second side edges and the top surface of thenotching layer with first and second corners respectively; and said ionmilling milling away said first and second corners.
 39. A method asclaimed in claim 38 including:each of the first pole piece layer and thenotching layer being formed with a ferromagnetic material with amagnetic moment; and the magnetic moment of the notching layer beinggreater than the magnetic moment of the first pole piece layer.
 40. Amethod as claimed in claim 39 wherein the first pole piece layer isformed of substantially Ni₈₀ Fe₂₀ and the notching layer is formed ofsubstantially Ni₄₅ Fe₅₅.
 41. A method of making a merged magnetic headthat has an air bearing surface (ABS) and a read head and a write headwherein the write head has a second pole tip layer that has a trackwidth at said ABS comprising:forming a first shield layer with an ABSsite that corresponds to said ABS; forming a first read gap layer on thefirst shield layer with an ABS site that corresponds to said ABS;forming a read sensor layer on the first read gap layer with an ABS sitethat corresponds to said ABS; forming a second read gap layer on theread sensor layer with an ABS site that corresponds to said ABS; forminga second shield/first pole piece layer with an ABS site that correspondsto said ABS, a track width site that is in alignment with a second poletip layer track width site which corresponds to said track width of thesecond pole tip layer and with top and bottom surfaces and first andsecond side edges that are outboard of the track width site of thesecond shield/first pole piece layer; forming a notching layer on thesecond shield/first pole piece layer with an ABS site that correspondsto said ABS, a track width site in alignment with said second pole tiplayer track width site and with top and bottom surfaces and first andsecond side edges that are inboard of the first and second side edges ofthe second shield/first pole piece layer but outboard of the track widthsite of the notching layer; forming a write gap layer on the notchinglayer and the second shield/first pole piece layer that has an ABS sitethat corresponds to said ABS and that has a track width site that alignswith said second pole tip layer track width site; forming a second poletip layer on the gap layer with an ABS site that corresponds to saidABS, a track width site that aligns with said second pole tip trackwidth site and with top and bottom surfaces and first and second sideedges that are inboard of the first and second side edges of thenotching layer but outboard of the track width site of the second poletip layer; ion milling the second pole tip layer, portions of the writegap layer and portions of the notching layer until the second pole tiplayer has milled first and second side edges that coincide with anddefine said track width; forming an overcoat layer on the secondshield/first pole piece layer and the second pole tip layer; and formingthe first shield layer, the first read gap layer, the read sensor, thesecond read gap layer, the second shield/first pole piece layer, thenotching layer, the write gap layer, the second pole tip layer and theovercoat layer with said ABS.
 42. A method as claimed in claim 41including:each of the first pole piece layer and the notching layerbeing formed with a ferromagnetic material with a magnetic moment; andthe magnetic moment of the notching layer being greater than themagnetic moment of the first pole piece layer.
 43. A method as claimedin claim 42 wherein the first pole piece layer is formed ofsubstantially Ni₈₀ Fe₂₀ and the notching layer is formed ofsubstantially Ni₄₅ Fe₅₅.
 44. A method as claimed in claim 41 wherein,before ion milling, each of the side edges of the notching layer extends0.10 μm to 1.0 μm beyond the track width site of the notching layer. 45.A method as claimed in claim 41 including:the forming of the notchinglayer forming the first and second side edges and the top surface of thenotching layer with first and second corners respectively; and said ionmilling milling away said first and second corners.
 46. A method asclaimed in claim 41 wherein, during ion milling, the write gap layer ismilled with first and second side edges that are contiguous with thefirst and second side edges respectively of the second pole tip layerand the notching layer is milled with first and second side edges thatare contiguous with the milled first and second side edges respectivelyof the write gap layer.
 47. A method as claimed in claim 46 wherein,before ion milling, each of the side edges of the notching layer extends0.10 μm to 1.0 μm beyond the track width site of the notching layer. 48.A method as claimed in claim 47 including:the forming of the notchinglayer forming the first and second side edges and the top surface of thenotching layer with first and second corners respectively; and said ionmilling milling away said first and second corners.
 49. A method asclaimed in claim 48 including:each of the first pole piece layer and thenotching layer being formed with a ferromagnetic material with amagnetic moment; and the magnetic moment of the notching layer beinggreater than the magnetic moment of the first pole piece layer.
 50. Amethod as claimed in claim 49 wherein the first pole piece layer isformed of substantially Ni₈₀ Fe₂₀ and the notching layer is formed ofsubstantially Ni₄₅ Fe₅₅.